Background: Prognosis and treatment of the first seizure depends on identification of a specific epilepsy syndrome, yet patients with first seizures are generally regarded as a homogeneous group. We studied whether it is possible to diagnose specific epilepsy syndromes promptly by use of standard clinical methods, electroencephalography (EEG) and magnetic resonance imaging (MRI).
Methods: 300 consecutive adults and children presented with unexplained seizures. We systematically collected clinical data from patients and witnesses, and attempted to obtain an EEG within 24 h of the seizure. Where the EEG was negative, a sleep-deprived EEG was done. MRI was done electively.
Findings: A generalised or partial epilepsy syndrome was clinically diagnosed in 141 (47%) patients. Subsequent analysis showed that only three of these clinical diagnoses were incorrect. Addition of the EEG data enabled us to diagnose an epilepsy syndrome in 232 (77%) patients. EEG within 24 h was more useful in diagnosis of epileptiform abnormalities than later EEG (51 vs 34%). Neuroimaging showed 38 epileptogenic lesions, including 17 tumours. There were no lesions in patients for whom generalised epilepsy was confirmed by EEG. Our final diagnoses were: generalised epilepsy (23% of patients); partial epilepsy (58%); and unclassified (19%).
Interpretation: An epilepsy syndrome can be diagnosed in most first-seizure patients. Ideally, an EEG should be obtained within 24 h of the seizure followed by a sleep deprived EEG if necessary. MRI aids diagnosis and should be done for all patients except for those with idiopathic generalised epilepsies and for children with benign rolandic epilepsy.